[Blood flow changes of cauda equina in experimental lumbar spinal canal stenosis under dynamic burden]

To study the changes of blood flow of the already-compressed cauda equina under dynamic burden, high frequency stimulation (HFS) and increased additional compression, and to clarify the mechanism of neurogenic intermittent claudication.

Thirty SD rats were divided into 5 groups, 6 in each. All groups were operated with laminectomy of the fifth lumbar verfebra. One hour after the measurement of blood flow, in 4 experimental groups, the silicon sheets were inserted into the spinal canal of L4 and L6 to cause double level compression of cauda equina by 30%. Two hours after onset of compression, no dynamic burden was introduced to the subjects of the experimental group 1. Only HFS was introduced to the subjects of the experimental group 2 for 6 minutes. Both HFS and increased additional compression were introduced to the subjects of the experimental group 3 for 6 minutes. While only increased additional compression was introduced to the subjects of the experimental group 4 for 6 minutes. The subjects of control group only underwent laminectomy of the fifth lumbar vertebra and HFS 6 minutes. The blood flow of cauda equina was measured with laser Doppler flowmeter.

In the first 2 hours, there was no significant change of cauda equina blood flow in the control group. During the time of HFS, the blood flow increased significantly to 186.4% +/- 31.5% of initial value (P < 0.05). In the experimental group 1, there was no blood flow change during the period of dynamic burden(110.4% +/- 7.5%, P > 0.05). After introduction of dynamic burden, there was no blood flow changes in the experimental group 2 (111.6% +/- 17.6%, P > 0.05). The blood flow in the experimental group 3 decreased to 65.3% +/- 10.7% of initial value (P < 0.05); and the blood flow in the experimental group 4 decreased to 60.1% +/- 9.2% of initial value (P < 0.01). There was no significant difference between the experimental groups 3 and 4 (P > 0.05).

The results above show that during the period of increased impulse transmission, double level compression of cauda equina may limit the increase of blood flow, which may cause relative ischemia. If there is increased additional compression along with increased impulse transmission, the blood flow will decrease significantly, which will cause absolute ischemia.